I don't know how your software works, so this may or may not be appropriate, but:

Open source the software. Promote it via a technical blog, Hacker News, meetups, and conferences. Become a thought leader in the GIS space. Keep running your service for people who don't want to worry about installing/running the software themselves. "Open Source for free, SaaS for pay" is a very valid business model, especially when selling to developers. Think of companies like Twilio or Sendgrid; I could set up my own Asterisk or SMTP server, or I could pay a low metered fee to have someone take away the headaches for me.

If you don't care enough about GIS to blog and speak about it, close up shop.